Feasibility of single-order parameter description of equilibrium viscous liquid dynamics

TL;DR

This study investigates whether a single parameter can effectively describe the equilibrium viscous liquid dynamics by analyzing molecular dynamics simulations of two glass-forming liquids, finding strong correlations supporting a single-parameter model.

Contribution

The paper provides molecular dynamics evidence that a single-parameter description can approximate the equilibrium viscous liquid dynamics for certain glass-formers.

Findings

Single-parameter description fits well for studied liquids.

Strong correlation between energy and pressure fluctuations.

Energy and volume fluctuations are also strongly correlated.

Abstract

Molecular dynamics results for the dynamic Prigogine-Defay ratio are presented for two glass-forming liquids, thus evaluating the experimentally relevant quantity for testing whether metastable-equilibrium liquid dynamics to a good approximation are described by a single parameter. For the Kob-Andersen binary Lennard-Jones mixture as well as for an asymmetric dumbbell model liquid a single-parameter description works quite well. This is confirmed by time-domain results where it is found that energy and pressure fluctuations are strongly correlated on the alpha-time scale in the NVT ensemble; in the NpT ensemble energy and volume fluctuations similarly correlate strongly.